1. Field of the Invention
This invention relates to the selective plasma chemical etching of polyimide-silicone copolymers for patterning thereof.
2. Description of the Prior Art
In the copending application of Abe Berger entitled "Polyimide-Silicone Copolymers For Coating Semiconductor Junctions", U.S. Ser. No. 652,092, filed Jan. 26, 1976, for the method of making the material and its application to selective surface areas of electronic devices is taught. After the copolymer material is applied to surface areas it becomes necessary on occasion to open windows in the coating and/or to remove material from selective areas. It is desirable that the removal of the unwanted portions of the copolymer material be done as quickly and as easily as possible to facilitate semiconductor device processing. It is also most desirable to maintain the registry and dimensions of the pattern.
In my copending patent application entitled "Novel Process for Selective Etching of Polymeric Materials Embodying Silicones Therein", Ser. No. 720,584, filed on Sept. 7, 1976, and now U.S. Pat. No. 4,140,572 I describe the use of titanium as a masking material for etching with a phenol-bearing solution. However, although the process is successful, one always finds a need for a more efficient process for a particular manufacturing requirement.
A novel process introduced into the semiconductor art is chemical etching by use of plasma. The plasma is an ionized gas containing a variety of highly reactive particles such, for example, as ions, free electrons and free radicals. An article entitled "A Survey of Plasma-Etching Process" appeared in Solid State Technology, May 1976, and describes the process.
An object of this invention is to provide a new and improved method to pattern a layer of a cured polyimide-silicone copolymer material.
Another object of this invention is to provide a new and improved method for selective plasma chemical etching of a layer of a cured polyimide-silicone copolymer material which embodies silicon as a masking material.
A further object of this invention is to provide a new and improved method for selective plasma chemical etching of a layer of a cured polyimide-silicone copolymer material which opens windows in the layer, the edges of which are substantially free of undercutting.
Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter.